Negative pressure wound closure device

ABSTRACT

The present invention relates to a negative pressure wound closure system and methods for using such a system. Preferred embodiments of the invention facilitate closure of the wound by preferentially contracting to provide for movement of the tissue. Preferred embodiments can utilize tissue grasping elements to apply a wound closing force to the tissue.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/243,320, filed Aug. 22, 2016, which is a continuation of U.S.application Ser. No. 13/942,493, filed Jul. 15, 2013 and now U.S. Pat.No. 9,421,132, which is a continuation-in-part of U.S. application Ser.No. 13/365,615, filed Feb. 3, 2012 and now U.S. Pat. No. 9,226,737,which claims the benefit of U.S. Application No. 61/439,525, filed Feb.4, 2011. U.S. application Ser. No. 13/942,493 also claims the benefit ofU.S. application Ser. No. 61/672,173, filed Jul. 16, 2012, U.S.application No. 61/679,982, filed Aug. 6, 2012, and U.S. Application No.61/779,900, filed Mar. 13, 2013. The entire contents of the aboveapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

A number of techniques have been developed for treatment of wounds,including wounds resulting from accident and wounds resulting fromsurgery. Often, wounds are closed using sutures or staples. However,inserting these mechanical closure techniques requires making additionalpunctures or wounds to the skin, which can result in tissue injury andin the case of excess swelling, possible ischemia and tissue loss. Also,mechanical wound closures such as staples and sutures can causehighly-localized stresses at the insertion points that can impede anddamage the normal wound healing processes of the skin.

In recent years, there has been increased interest in using negativepressure devices for the treatment of wounds. Negative pressure woundtreatment utilizes devices that remove wound fluids by applying negativepressure suction to the wound. It is believed that such negativepressures promote wound healing by facilitating the formation ofgranulation tissue at the wound site and assisting the body's normalinflammatory process while simultaneously removing excess fluid, whichmay contain adverse cytokines bacteria. However, further improvements innegative pressure wound therapy are needed to fully realize the benefitsof treatment.

SUMMARY OF THE INVENTION

The present invention relates to a negative pressure wound closuredevice that specifically exerts force at the edges of the wound tofacilitate closure of the wound. The device operates to reduce the needfor repetitive replacement of wound filler material currently employedand can advance the rate of healing. The device simultaneously usesnegative pressure to remove wound fluids and to assist in closure of thewound.

In one embodiment, a negative pressure wound closure device includes awound filler material that is sized and shaped to fit within a woundopening and which contracts along at least one dimension uponapplication of a negative pressure to the filler material. The fillermaterial is thus configured to preferentially contract in at least onedirection and inhibit contractions in one or more additional directions.Prior negative pressure devices did not assist in wound closure, butwere used to drain fluids. By providing for the controlled movement oftissue during the healing process in conjunction with the drainage offluids from wounds as described in connection with the presentinvention, a substantial improvement in the rate of healing can berealized. Note that depending on the size of the wound, increasednegative pressure can be used.

In another preferred embodiment, a tissue grasping surface extends overan outer peripheral surface of the wound filler material and includes aplurality of tissue anchors that engage the tissue at the wound margin.Upon application of negative pressure, the tissue at the wound margin isdisplaced to facilitate closure of the wound. A negative pressuresource, such as a vacuum pump, is coupled to the wound filler materialto provide the negative pressure.

The wound filler material generally comprises a porous material, such asa foam. For embodiments employing tissue anchors, these can beintegrally formed in the filler material. In other embodiments, thetissue anchors are provided on a separate covering or film that issecured to the filler material.

In preferred embodiments, the filler material includes a stabilizingstructure that enables the material to collapse in at least one firstdirection and inhibits collapse in at least one second direction. Thestabilizing structure can include regions of relatively rigid materialsurrounded by regions of relatively compressible material. In preferredembodiments, the stabilizing structure is an endoskeleton formed ofrigid and/or semi-rigid materials.

In exemplary embodiments, the regions of compressible material mayinclude one or more sections of a compressible material configured,e.g., sized and shaped, for association with one or more surfacesdefined by the stabilizing structure. For example, a stabilizingstructure may define a top surface, a bottom surface and one or moreside surfaces each, of which being associated with a correspondingsection of a compressible material. In exemplary embodiments, eachsection of the compressible material can be configured, e.g., sized andshaped, to match the corresponding surface. Thus, the sections ofcompressible material cooperate to envelope the stabilizing structure,e.g. to facilitate structural characteristics as described in thepresent application. In some embodiments, a tissue grasping surface,such as described above, may extend over an outer peripheral surface ofthe compressible material, e.g. of the side sections of the compressiblematerial that can engage the wound margins of an open wound.

In exemplary embodiments the sections of compressible material candefine a plurality of surface features on the inner peripheral surfacesthereof. For example ,the sections of compressible material may definean “egg crate” pattern of ridges and valleys. Advantageously, thesurface features defined on the inner peripheral surface of the sectionsof compressible material can be configured for operative associationwith an inner volume of stabilizing structure. In exemplary embodiments,each surface of the stabilizing structure may define a lattice patternof stabilizer elements. Thus, the surface features defined on the innerperipheral surface of each section of compressible material may beconfigured, e.g., patterned, to match the lattice pattern of thecorresponding surface of the stabilizer element. In exemplaryembodiments, the surface features defined on the inner peripheralsurface of each section may provide tensile forces to the stabilizingstructure, e.g., during the collapse thereof, to facilitate a structuredcollapse, e.g., in one or more directions. In some embodiments, thesurface features defined on the inner peripheral surface of each sectionmay be configured to impart a pre-selected force profile to thestabilizing structure, e.g., during the collapse thereof. In someembodiments, a pre-selected force profile can control the collapse ofthe stabilizing structure, e.g., providing for a non-uniform collapsesuch as by resisting collapse in one or more directions and/or in one ormore regions. The shaped wound filler material provides for fluidtransport across the device during the application of negative pressure.Consequently, a preferred embodiment provides for continuous contact ofwound filler elements to facilitate continuous flow of fluid from thetissue margins and underlying tissue to the fluid exit port(s) fordrainage from the wound.

In certain embodiments, the stabilizing structure inhibits the fillermaterial from collapsing along its height dimension, while enabling thefiller material to collapse within the plane defined by the woundmargins. This is useful in the case of abdominal surgery, for example,in which the surgical incision is along a straight line and openslaterally to form an oval shaped wound. This generally oval shaped woundcan extend through muscle and fatty tissue having variable mechanicalproperties. Wound healing is better served through the use of an ovalshaped structure adapted to preferentially collapse towards the originalline of incision. In preferred embodiments, the stabilizing structurepromotes collapse of the filler material in a manner to effectreapproximation of the wound tissue. Fasciotomy wounds, or other wounddehiscences, or any open wound can be successfully treated usingembodiments of the present invention.

The wound closure device can be used to treat wounds in the mediastinum,for pressure ulcers, for wounds in the extremities (arms or legs) etc.The wound closure device can also be used to treat wounds of differentshapes, such as circular, square, rectangular or irregularly shapedwounds. A plurality of wound closure elements can be shaped to fitwithin a wound and can attach together to preferentially close the woundin a desired direction. The different elements can comprise differentmaterials or have different characteristics, such as pore size and/oranchor size and distribution to form a composite structure.

In one embodiment, an endoskeleton stabilizing structure includes aplurality of spaced-apart rigid members forming a cross-hatchedconfiguration. The endoskeleton enables the filler material to collapsealong its width dimension and elongate to a smaller degree along itslength dimension. In certain embodiments, a plurality of rigid membersextend along the height of the filler material and inhibit collapse ofthe material in its height dimension, for example. According to certainembodiments, the endoskeleton comprises a network of interconnectedrigid members that can articulate with respect to one another duringcollapse of the filler material. The endoskeleton can include trusssupports to inhibit tilting motion of the filler material. In someembodiments, the tissue anchors can be integrally formed in theendoskeleton. The endoskeleton can have flexure elements with elasticproperties such that the lateral force imparted by the skeleton is afunction of displacement. The endoskeleton or frame prevents tilting ofthe wound closure device during use. The frame can include hollow tubesor cavities that alter the flex characteristics of the frame. The tubesor cavities can be used for the delivery of media into the wound.

A preferred embodiment of the invention utilizes a wound healing devicefor the treatment of wounds in which seromas can form. The wound healingdevice can include apertures to provide for tissue contact through theapertures to promote wound healing. The device can include removalabledrain elements for the application of negative pressure.

In certain embodiments, the wound filler material includes a smoothbottom surface having micropores to allow the passage of fluid from thewound through the bottom surface and into the device for removal. Themicropores can have variable pore size and/or pore density to direct thedistribution of vacuum force from the negative pressure source. In someembodiments, the wound filler material can have variable internal poresizes and/or pore density to direct the distribution of vacuum force.

In one embodiment, a negative pressure wound treatment component formanaging and/or removing fluid is coupled to the wound filler material.A single negative pressure source can be used for wound closure andfluid management/drainage. A sliding surface is provided at theinterface between the wound closure and fluid management components.

In yet another embodiment, the filler material includes removableportions to adjust the size of the wound closure device. The fillermaterial can be provided with pre-determined cleavage lines for tearingor cutting away portions of the material. In certain embodiments, setsof tissue anchors are embedded in the filler material, and becomeexposed by removing excess portions of the material.

According to another embodiment, the tissue anchors are provided with avariable force profile. The force profile can vary based on the depth oftissue or the type of tissue engaged. In some embodiments, the forceprofile of the tissue grasping surface varies around the perimeter ofthe wound closure device. The force profile is varied, for instance, byvarying one or more of the length of the tissue anchors, the shape ofthe anchors, the materials of the anchors and the density of theanchors.

The present invention also relates to methods of closing a wound using awound closure device as described above. For example, a linear incisionin the skin overlying the abdomen provides access to a surgical sitesuch as the gastrointestinal system of the human or animal body.Following completion, the wound must be treated by negative pressuretherapy to facilitate recovery. Thus, a wound closure device inaccordance with preferred embodiments of the invention is inserted forwound closure treatment.

In a preferred embodiment, the wound closure device does not includetissue anchors, but instead utilizes a structure having a shape memorysuch that it expands to fill the wound cavity. Thus, the expanding frameexerts an expansion force when compressed so that the lateral peripheralelements of the device maintain contact with the wound margins aroundthe peripheral surfaces of the wound closure device. The laterallydirected outward expansion force is less than the closure force exertedon the tissue upon application of negative pressure that operates toclose the wound margins and compress the wound closure device.

By using the negative pressure wound closure device of the invention,patients with large or severe wounds are able to be discharged or engagein rehabilative physical therapy, changed at home and then brought backto have their wounds simply stitched closed. By improving wound closuretreatment and thereby reducing cost, there is an opportunity for thesedevices to be a significant part of the instruments used for wound care.

A preferred embodiment of the invention uses a wound healing device incombination with a wound closure device for treatment of woundsrequiring both components.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be apparentfrom the following detailed description of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1A is a perspective schematic view of a negative pressure woundclosure device.

FIG. 1B is a cross-section view of the tissue grasping surface of thewound closure device.

FIG. 1C is a side view of one embodiment of the tissue grasping surface.

FIG. 1D is a top view of the wound closure device showing x-ystabilizers in phantom.

FIG. 1E is a cross-section view of filler material showing x-ystabilizers and z-stabilizers.

FIG. 1F is a bottom view of the wound closure device showing a smoothbottom surface and micropores for removing fluid from the wound site.

FIG. 1G is an elevation view of a peripheral stabilizer element.

FIGS. 2A and 2B are perspective and side views, respectively, of asupporting endoskeleton.

FIGS. 3A and 3B are perspective and side views, respectively, of asupporting endoskeleton with support trusses.

FIG. 3C is a side view of a supporting endoskeleton with x-shapedsupport trusses.

FIGS. 4A-C illustrate a wound closure device of the invention closing awound.

FIGS. 4D-4E illustrate the use of a plurality of wound closure elementsused for wounds of different shapes.

FIG. 5 illustrates a two-stage negative pressure wound treatment andnegative pressure wound closure (NPWT/NPWC) device.

FIG. 6 illustrates an enlarged view of a preferred embodiment of thetissue anchor system in accordance with the invention.

FIG. 7 illustrates an embodiment of a wound filler material having atear-away or cut-away design for accommodating different wound sizes,with tissue anchors embedded within the filler material atpre-determined cleavage points.

FIG. 8A is a side view of a tissue grasping surface, illustratingdifferent tissue anchors for different types of tissue (T₁, T₂) and therespective force profiles for the anchors, including the maximum forceapplied during vacuum closure (F₁) and the force required to remove theanchors from the tissue (F₂) without damaging the tissue.

FIG. 8B illustrates different designs for a tissue anchor of theinvention.

FIG. 8C illustrates an enlarged view of tissue anchor elements on theperipheral surface of an oval shaped wound closure device.

FIG. 9A is a schematic illustration of a wound closure device positionedwithin a wound showing the different force profile around the margin ofthe wound according to one embodiment.

FIG. 9B illustrates the wound closure device of FIG. 9A after a periodof wound closure and healing, with the original configuration of thewound and wound closure device indicated in phantom.

FIGS. 10A and 10B schematically illustrate processes of using a woundclosure device in accordance with preferred embodiments of theinvention.

FIG. 11A illustrates a cross sectional view of a wound drain and closuresystem at a surgical site in accordance with a preferred embodiment ofthe invention.

FIG. 11B illustrates a top view of a wound closure device and a tissueadhesion device.

FIG. 11C shows a detailed perspective of a surgical drainage system inaccordance with a preferred embodiment of the invention.

FIG. 12 illustrates a cross-sectional view of wound drain and closuresystem used for a surgically treated pressure ulcer in accordance with apreferred embodiment of the invention.

FIG. 13 illustrates a sensor system for measuring the wound closureforce for a negative pressure wound closure system.

FIG. 14 illustrates a pressure sensor system for measuring woundpressure in accordance with preferred embodiments of the invention.

FIG. 15 illustrates a negative pressure wound closure system having acontrolled pressure system.

FIGS. 16A and 16B illustrate perspective and exploded views of apreferred embodiment of the device.

FIG. 17 shows a perspective view of the assembled device of FIG. 16B.

FIGS. 18A and 18B show discrete shaped elements of the wound fillerwithin the associated structure.

FIG. 19 illustrates an outer layer with tissue anchor elements.

FIGS. 20A and 20B show the anchor elements adhering to tissue.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A-1F illustrate an embodiment of a wound closure device 100 ofthe present invention. The device 100 includes a wound filler material102 that is sized and shaped to fit within a wound opening of a human oranimal patient. In preferred embodiments, the filler material 102 is aporous, biocompatible material, such as an open cell polyurethane foam.The filler material 102 is also preferentially collapsible, meaning thatits size can be reduced along at least one dimension (e.g., length,width, height) by applying a negative pressure to the filler material102, while at the same time inhibiting contractions or contracting at aslower rate in another direction. Further details regarding devices andmethods of the present invention can be found in U.S. application Ser.No. 13/365,615 filed on Feb. 3, 2012, the entire contents of which isincorporated herein by reference.

Extending over at least one surface of the filler material 102, andpreferably extending over an outer perimeter surface of the fillermaterial 102 is a tissue grasping surface 104. In one embodiment, thetissue grasping surface 104 is a flexible covering, such as a mesh film,that is secured to the outer perimeter surface of the filler material102 and can expand and contract with the expansion and contraction ofthe filler material 102. In one embodiment, the tissue grasping surface102 is a mesh film or a composite polyester mesh film, such as theParietex™ mesh from Covidien (Mansfield, Mass.). The tissue graspingsurface 104 includes a plurality of outward-facing tissue anchorelements 106, which in the preferred embodiment are a plurality ofclosely-spaced barbs, hooks or tissue grasping elements, which can beintegrally formed in the mesh film.

FIG. 1B is an edge view of the device 100 showing the tissue graspingelements 106 projecting from the tissue grasping surface 104 on theperiphery of the wound filler material 102. FIG. 1C is a side view ofone embodiment, in which the tissue grasping surface 104 is formed froma flexible material, in particular, a mesh material. The graspingelements 106 project out from the page in FIG. 1C. The flexible, meshmaterial of the tissue grasping surface 104 allows the surface to expandand contract as necessary with the expansion and contraction of theunderlying wound filler material 102.

In other embodiments, the tissue grasping surface 104 with anchorelements 106 can be integrally formed in the filler material 102. Thetissue grasping surface and/or anchor elements can also be formed usinga resorbable material.

The tissue anchor elements 106 are preferably provided over an entireouter perimeter surface of the filler material 102. When the fillermaterial 102 is placed within a wound, the anchor elements 106 becomeburied within the tissue at the wound margins and secure the device 100within the wound opening. The tissue anchor elements 106 are preferablyspread out over the entire surface of the wound margin to providesufficient strength in the grasping force. The tissue grasping surface104 is preferably designed to allow the wound closure device 100 to beeasily placed but also easily removed and replaced with a new device 100or other wound dressing as needed (e.g., 2-7 days later). The graspingsurface 104 can be configured to have high grasping strength over atleast a portion of its surface, but easily removable by, for example,pulling away at an edge. The tissue grasping surface 104 is preferablydesigned to be removed from a wound without damaging the surroundingtissue. The anchor elements 106 are preferably designed to accommodatevarious tissue applications, such as muscle, fat, skin and collagen, andvarious combinations of these. The anchor elements 106 can also bedesigned to remain securely attached to particular tissues for aselected time period in certain embodiments.

In embodiments in which the grasping surface 104 is formed from acovering on the outer peripheral surface of the filler material 102, thegrasping surface can be attached to the filler material 102 using anysuitable technique, such as with an adhesive or a mechanical fasteningsystem. In a preferred embodiment, the tissue grasping surface 104includes filler-grasping anchor elements, which can be barbs, thatsecure the grasping surface to the filler material. As shown in thecross-section view of FIG. 6, for example, the grasping surface 400comprises a thin mesh or film having two sets of barbs or similar anchorelements, a first set 410 of outwardly-facing tissue-grasping elements412 that are designed to project into tissue, and a second set 404 ofelements 406 that project into the filler material to secure thegrasping surface to the filler material.

Returning to FIGS. 1A-1F, a negative pressure source 120, such as apump, is coupled to the filler material 102 by a suitable coupling orconduit, such as tube 121. Additional tubes 107 can also be connectedthrough an array of spaced ports 105 in order to spatially distributethe suction force so that the force exerted along the sidewall 104 canbe controlled separately from a fluid suction force. The negativepressure source 120 can be activated to apply a negative pressure to thefiller material 102. In general, the negative pressure causes aresulting pressure differential which causes the filler material 102 tocontract or “collapse.” As the filler material 102 contracts, the tissuegrasping surface 104 grabs and pulls on the adjacent tissue, which ispreferably the tissue around a wound margin, resulting in thedisplacement of the tissue thereby facilitating the closure of thewound. In a preferred embodiment, the filler material 102 is designed tocollapse preferentially in at least one direction. For example, in theembodiment of FIG. 1A, the filler material 102 includes a length andwidth dimension along the y- and x-axes, respectively, and a heightalong the z-axis. In order to efficiently transmit the negative pressureto the subcutaneous or other wound margins, it is preferred that thefiller material 102 does not collapse centrally in the z-direction (likea pancake), so that the action of the negative pressure workspredominantly in the x-y directions, or more particularly, in atwo-dimensional plane along the wound margins such as in an open abdomenor fasciotomy. It will be understood that in some embodiments, the planeof the wound margins can be curved, such as when the wound goes aroundthe curve of an abdomen or leg.

Furthermore, in preferred embodiments the filler material 102 isconfigured to preferentially collapse in length and/or width (i.e.,along the x- and y-axes) to reapproximate the tissue at the woundmargins. Note that certain types of wounds can be treated without theanchor elements described herein.

There are several ways in which the filler material 102 is configured toexhibit preferential collapse characteristics. For example, portions ofthe filler material 102 can be made from more rigid material than thesurrounding material, causing the filler material to preferentiallycollapse in a particular direction. In one embodiment, the fillermaterial 102 can include a stabilizing endoskeleton made from a suitablerigid material embedded within a “collapsible” filler, such as an opencell foam. Note that the amount of applied negative pressure can beadjustable depending on the size and shape of the wound. Pressures above125 mm, to as much as 250 mm or more can be used to assist in woundclosure. The pressure can be reduced over time as the wound contracts.

As shown in FIGS. 1D and 1E, for example, the filler material 102includes a plurality of stabilizer elements 108 (shown in phantom) thatenable the collapse of the filler material in certain directions, whileinhibiting it in other directions. In this embodiment, the stabilizerelements 108 include a plurality of stabilizing ribs, flexures or rods,made from a suitably rigid or semi-rigid material, such as plastic. Theribbed structure is configured to preferentially collapse along aspecific axis to facilitate proper closure of the wound. The internalstabilizer elements 108 in this embodiment form a cross-hatched patternas seen in FIG. 1D, though it will be understood that otherconfigurations can be utilized. The spacing between the elements in the“open” state can be in a range of 1-2 cm, for example. The stabilizerelements 108 can be provided at different depths within the fillermaterial, as shown in the cross-section view of FIG. 1E, which helpsinhibit collapse in the z-direction. In some embodiments, z-axisstabilizer elements 110 can be utilized to inhibit collapse in thisdirection. In FIG. 1E, the z-axis stabilizer elements 110 areprojections that extend vertically from the ribs 108. In otherembodiments, separate z-axis stabilizers, such as rods or ribstructures, can be employed.

In certain embodiments, the device 100 can include a flexible coveringcomprising peripheral stabilizer element 111 that extends around theouter periphery of the filler material 102, as shown in FIG. 1E. Thestabilizer element 111 can include a rib structure that reinforces thefiller material 102 in order to prevent collapse in the z-direction, aswell as to inhibit tilting of the filler material in the z-y and z-xplanes. Thus, preferred embodiments of the filler materialpreferentially contract in at least a first direction relative to asecond direction upon application of a negative pressure. Thus, forexample, the width will contract at a faster rate relative to thelength, while the height (depth of the wound) does not contract asubstantial distance.

In some embodiments, the tissue grasping anchor elements 106 can beincluded on the peripheral stabilizer element 111, and project out fromthe periphery of the filler material 102. This can be as an alterativeto, or in addition to, providing the anchor elements 106 on a separatemesh or film. The peripheral stabilizer element 111 is preferablyconfigured to expand and contract as necessary with the expansion andcontraction of the wound filler material 102. Thus, in a preferredembodiment, the stabilizer element 111 has sufficient flexibility tocontract and expand in the x- and y- directions (i.e., around theperiphery of the filler material 102), but has adequate rigidity alongthe z-direction (i.e. along the height of the filler) to inhibitcollapse or tilting in this direction.

An embodiment of a peripheral stabilizer element 111 is shown inelevation view in FIG. 1G. The stabilizer element 111 includes aplurality of stabilizing rods 113, oriented to inhibit collapse in thez-direction. The rods 113 are separated by a flexible material 114 thatallows the stabilizer element 111 to expand and contract around thewound margin with the expansion and contraction of the underlying fillermaterial. In this embodiment, the tissue anchor elements 106 are formedin the peripheral stabilizer element 111 and project out from the page.

One embodiment of an endoskeleton for a wound filler material of theinvention is shown in FIGS. 2A and 2B. The endoskeleton includes a firstset of x-y stabilizer elements 108 a and a second set of x-y stabilizerelements 108 b that are connected by a plurality of z-axis stabilizerelements 110. During collapse of the filler material 102, the respectivex-y stabilizer elements 108 a, 108 b are collapsible in the x-ydirections, but the z-axis stabilizer elements 110 inhibit collapse inthe z-direction. In preferred embodiments, the stabilizer elements canarticulate with respect to one another during collapse. The joints 109in the structure can be hinged or have a reduced thickness toaccommodate the flexing of the system. The flexures between the jointsmay also flex to accommodate the desired compression along the first, orlateral, axis 117 (see FIG. 4B). Some expansion can occur along thesecond, or longitudinal, axis 119 as the device compresses. The framematerial can have a shape memory characteristic, which in combinationwith the suction force, 25 defines the force level applied to thetissue.

In another embodiment, shown in FIGS. 3A and 3B, the endoskeletonincludes truss stabilizers 112 to inhibit tilting of the filler material102 during collapse. The truss stabilizers 112 keep the upper 108 a andlower 108 b x-y stabilizers aligned with one another as the fillermaterial 102 collapses. In some embodiments, the truss stabilizers 112can be rigid in certain directions and relatively less rigid in otherdirections (for example, the truss stabilizer can be bowed) to promotecollapse in certain directions. FIG. 3C illustrates an alternativeembodiment having truss stabilizers 112 in an “x”-shaped pattern.

A preferred embodiment of the present invention employs an endoskeletonstructure in which one or more of the stabilizer or flexure elements108, 112 comprise hollow tubes or cavities 115. The hollow tube elements108, 112 can be used to alter the elastic characteristics of thestructure and thereby adjust the lateral displacement and forcecharacteristics of structure. The diagonal flexures 112 extend betweenthe planes formed by the lateral elements 108 a and 108 b.

The use of hollow tube elements in the elastic structure can also beused for the delivery of drainage fluid, medication, oxygen or othermedia into the wound. The tubes 108, 112 can contain media upon implantinto the wound that is subsequently released into the wound or can beconnected to an external source. The tube walls can have pores that opento accommodate fluid flow into the wound from within the tube elementsor cavities therein. The location of tubular elements, as opposed tosolid rods or flexures, can be selectively positioned within thestructure depending on the preferred delivery location. For example, theflexures 108 along the lateral walls can be used for delivery to theregions being drawn together under negative pressure. Alternatively, theflexures in the bottom plane of the skeleton can be used for delivery tothe underlying tissue structure or organs.

The stabilizing endoskeleton in certain embodiments can be made, inwhole or in part, from a shape memory material. Various shape memorymaterials can be used which return from a deformed state (temporaryshape) to their original (permanent) shape. This change in shape can beinduced by an external stimulus or trigger. In one embodiment, theoriginal or “permanent” shape of the endoskeleton is the “collapsed”configuration of the wound closure device, or the shape that will bringabout wound reapproximation. When the wound closure device is initiallyinserted in the wound opening, the endoskeleton is in a deformed ortemporary state and embedded within the filler material. Theendoskeleton can preferentially revert to its original or “collapsed”state or, alternatively, cause the device to expand to engage thetissue. The “collapse” force of the shape memory endoskeleton can be inaddition to or an alternative to the vacuum force induced by thenegative pressure source. In certain embodiments, the application of anegative pressure to the wound closure device, which can cause theendoskeleton to revert to its original state.

FIG. 1F shows the bottom of the wound closure device 100 according toone embodiment. The device 100 in this embodiment includes a smoothbottom surface 115. This material can be biocompatible film to be usedwith, such as, provided in conjunction with the Renasys® systemavailable from Smith & Nephew. A preferred embodiment can also be usedwith a gauge as also provided in the Renasys® system. The bottom surface115 provides a low-friction interface between the wound closure device100 and the underlying tissue. In the case of an abdominal wound, forexample, the underlying tissue can include internal organs, such as theintestines. The smooth bottom surface 115 enables the filler material102 to contract and expand freely without interference from theunderlying tissue, and without damaging the underlying tissue. In apreferred embodiment, the bottom surface 115 includes micropores 116(shown with size exaggerated in FIG. 1F for purposes of illustration)that allow the passage of fluid through the bottom surface 115 and intothe device 100 for removal from the wound site. The wound closure devicecan also be inserted over a separate layer of material so that thedevice with contract on top of the sliding layer.

In some embodiments, the micropores 116 can have different sizes indifferent regions and/or can have different pore densities in differentregions in order to direct different force levels of the vacuum sourceto different regions of the device 100. Similarly, the filler material102 can be engineered with different internal pore sizes and/or poredensities to direct the distribution of forces from the vacuum source todifferent areas of the device 100.

FIGS. 4A-4C illustrate the use of the present device 100 to close awound 200. The wound 200 includes a wound opening 201 and a wound margin203, as shown in FIG. 4A. In FIG. 4B, a wound closure device 100 isplaced within the wound opening 201 so that the tissue grasping surface104 is contacting the wound margin 203. In certain embodiments, thewound closure device 100 can be formed by trimming or tearing the fillermaterial 102 to the proper size, and then attaching the tissue graspingelements 106 around the periphery of the filler material 102. In oneembodiment, the grasping elements 106 are attached by attaching atwo-sided barbed mesh to the filler material 102, where theoutward-facing prongs are designed for grasping tissue and theinward-facing prongs are designed to secure the mesh to the fillermaterial 102. A tube 121 connects the filler material 102 to thenegative pressure source. The area of the wound 200, including thefiller material 102, can be covered by a sealing drape 205.

In the embodiment of FIG. 4B, the filler material 102 includes aplurality of internal stabilizer elements 108 (shown in phantom) thatprovide the filler material 102 with a preferential collapsecharacteristic. The stabilizer elements 108 help control the collapse ofthe filler material 102, and the resulting displacement of the tissuearound the wound margin 203, in the x- and y-directions. Additionalstabilizer elements can be provided to control or inhibit collapse alongthe z-direction. As described above in connection with FIGS. 1D, thestabilizer elements 108 in this embodiment include a crosshatchedconfiguration.

FIG. 4C illustrates the wound 200 following the application of anegative pressure to the wound closure device 100. The tissue anchorelements 106 grab the tissue margins 203 and cause displacement of thetissue margins 203 as the filler material 102 collapses. As seen in theFIG. 4C, the filler material 102 collapses in the x- and y- directionsin such a manner as to reapproximate the tissue at the wound margin 203.In the embodiment of FIG. 4B and 4C, the crosshatched configuration ofthe stabilizer elements 108 help control the direction of tissuedisplacement during collapse. The largest amount of tissue displacementin this embodiment is in the central region of the wound 200, where theopening 201 is widest, and this displacement is primarily inward alongthe x-direction. Away from the central region (e.g., at the top andbottom of the wound as shown in FIGS. 4A and 4B), where the woundmargins are closer together, less displacement in the x-direction isneeded to reapproximate the tissue.

In general, the inward collapse of the filler material along they-direction is undesirable. In fact, during tissue reapproximation, thewound 200 will tend to elongate in y-direction as the wound marginsclose in the x-direction. In preferred embodiments, the internalstabilizer elements 108 promote the collapse of the filler material in amanner that provides wound reapproximation. In the embodiment of FIGS.4-C, for example, during filler collapse the crosshatched stabilizerelements 108 straighten out relative to one another, similar to anaccordion gate. The largest displacement is in the central region of thefiller 102, along the x-direction. The stabilizers 102 generally inhibitinward collapse along the y-direction. As the stabilizers 108 straightenout, they can also facilitate elongation of the wound in the y-directionto allow proper tissue reapproximation. Shown in FIGS. 4D-4E aredifferent shaped wounds 220, 240 in which a plurality of wound closureelements are used in combination to fill the wound. In FIG. 4D, elements222, 224, 226 and 228 have different shapes that are cut or trimmed tosize so as to substantially fill the wound that in this example, iscircular in shape. When negative pressure is applied, the elements worktogether to close the wound in a desired direction. FIG. 4E illustratesa rectangular wound 240 using closure elements 242, 244, 246, 248 and250 to fill the wound 240. The tissue anchors of each closure elementcan also attach to the adjoining closure element(s). With suctionapplied to the central elements 224, 250, the adjoining elements aredrawn towards the central elements to close the wound.

The wound closure device 200 can remain in this configuration for aperiod of several days or weeks to facilitate closing and healing of thewound 200. After a period of healing, the device 100 can be removed andoptionally replaced with a smaller device. After the wound has beensufficiently closed using the present device, it can be stitched closed.

FIG. 5 illustrates a two-stage negative pressure wound treatment andnegative pressure wound closure (NPWT/NPWC) device 300. The deviceincludes a negative pressure drainage/fluid management component 301, asis known in the art, that connects with an overlying negative pressurewound closure device 100. The wound closure device 100 includes acollapsible wound filler material 102 and a tissue grasping surface 104,substantially as described above. A tube 121 connects the device 300 toa single pump for applying a negative pressure to the wound closure andwound treatment components. The device 300 can include interchangeableparts depending on the need of a specific wound application. In oneembodiment, the device 300 is used for abdominal wounds in one example,and can also be used for mediastinum and fasciotomy wounds.

In a preferred embodiment, the filler material 102 is able to “slide”within the total NPWT/NPWC device 300. The filler material 102 includesa sliding surface 303 at the interface between the wound closure andfluid management components. The sliding surface can comprise a treatedsurface or a separate layer of material. The sliding surface 303facilitates the free contraction of the wound closure component, withoutinterference from the fluid management component. The underlying fluidmanagement component 301 can be specifically configured to manage fluidonly and to not generate granulation, as this can slow down or inhibitthe “slide.”

FIG. 6 illustrates an enlarged view of a preferred embodiment of thetissue anchor system 400 in accordance with the invention. One side ofthe material 402 has a first group of anchor elements 404 that areadapted to grasp the filler material. The first anchor elements 404 canbe shaped to grasp the filter material such as with a distal hookedshape 406. As material 402 must attach to the filter with a certaingrasping strength in order to apply a sufficient pulling force on thetissue, a specified force level F, must be applied to remove the hooksfrom the filler material that exceeds the pulling force being applied tothe tissue. Similarly, as the tissue to be grasped by the material 402has different structural characteristics then the filler material, asecond group of anchor elements 410 adapted to grasp tissue can have adifferent shape and grasping force then the first anchor elements. Inthis embodiment, barbs 412 can have bilateral prongs 414 that tend tocollapse upon insertion in tissue and yet expand when pulled in anopposite direction such that a certain pulling force can be applied totissue. However, the prongs or cone shape anchor element has a releaseforce such that the barbs can be manually pulled from the tissue withoutcausing injury.

FIG. 7 illustrates an embodiment of a wound filler material 500 having atear-away or cut-away design for accommodating different wound sizes.The filler material 500 includes natural cleavage lines 501, 503, 505that allow the size of the material to be adjusted to fit the wound tobe closed. The material 500 is designed to be torn or cut at thecleavage lines to remove one or more portions 502 a, 502 b, 502 c of thematerial and adjust the size of the material. Sets of tissue anchors 506a, 506 b, 506 c, 506 d are embedded within the filler material atpre-determined cleavage points, and become exposed as the respectiveouter portions 502 a, 502 b, 502 c are removed. The tissue anchors 506a, 506 b, 506 c, 506 d can be associated with a stabilizing endoskeletonstructure, such as described above in connection with FIGS. 1-4. In someembodiments, the stabilizing endoskeleton structure can includepre-defined cleavage or attachment points to remove portions of thestabilizer structure as the size of the filler material 500 is adjusted.

FIG. 8A is a side view of a tissue grasping surface, illustratingdifferent tissue anchors 601, 602, 603, 604 for different types oftissue (T₁, T₂). Also illustrated is an example of the respective forceprofiles for the anchors, including the maximum force applied to thetissue during vacuum closure (F₁) and the force required to remove theanchors from the tissue (F₂) without damaging the tissue. In oneembodiment, the characteristics of the tissue anchors vary to providedifferent force profiles across the interface between the wound closuredevice and the surrounding tissue. For example, for the upper tissuelayer(s), T₁, the anchor 601 is designed to attach to collagen material,such as in the dermis. The anchor 601 has a different force profile (F₁and F₂) on the upper tissue layer(s), T₁, as shown in FIG. 8A. At thelower tissue layers T₂, the anchors 602, 603, 604 are designed to attachto fatty tissue of subcutaneous layer. Generally, a smaller forceprofile is needed to secure the anchors to this tissue.

The characteristics of the anchors, and their resulting force profiles,can vary by a number of parameters, such as the length of the anchor,the shape of the anchor, the structure of grasping features, thematerial(s) used for the anchor, the relative flexibility/rigidity ofthe anchors, and the spacing/density of the anchors. In FIG. 8A forexample, anchor 601 is significantly longer than anchors 602, 603, whichin turn are longer than anchors 604. FIG. 8A also illustrates varyingthe density of anchors, such as shown in 602, 603 and 604. FIG. 8Billustrates three examples of different types of grasping features,including a barbed configuration 605, a staggered hook configuration606, and a staggered barbed configuration 607. Other suitable graspingfeatures can be utilized such as the anchor elements 620 shown in theenlarged perspective view of FIG. 8C. The anchoring process can beaugmented by suturing the filler material or supporting endoskeleton tothe tissue. The force profile can also be varied by controlling thevacuum force distribution in the filler material, such as by varying thepore size and/or pore density of the filler.

The wound closure device of the invention can be provided in kits forclosing different types of wounds (e.g., abdominal, fasciotomy, etc.).The tissue grasping surface can be optimized for different types oftissue such as collagen, fatty tissue and muscle, depending on thestructure of the tissue at the wound site.

In certain embodiments, the force profile of the wound closure device isvariable around the periphery of the wound. An exemplary embodiment isillustrated in FIG. 9A, which shows the force profile (f₁) exerted onthe wound margins at a plurality of locations on the periphery of thewound. In this embodiment, the largest f₁ is at the central region ofthe wound filler 102, where the wound opening is widest and the woundclosure force is entirely or nearly entirely in the x-direction. Movingtowards the top and bottom regions of the wound, the closure force (f₁)is much smaller. One reason for this is because the wound opening ismuch smaller in these regions, and a much smaller force is needed toreapproximate the tissue. Also, the inward force exerted in theseregions includes components in both the x- and y-directions. Thus, asmaller force profile is preferable to avoid the inward collapse of thetissue in the y-direction. As illustrated in FIG. 9B, as the woundcloses and heals from an initial state (indicated by dotted lines) to alater state (indicated by solid lines), it becomes elongated in they-direction. Thus, the displacement of tissue anchors 701 a and 701 b isexclusively in the x-direction and in the direction of the closure force(f₁), while the displacement of tissue anchors 703 a, 703 b is bothinwards in the x-direction (in the direction of the closure force) andoutwards in the y-direction (opposite the direction of the closureforce). Thus, a smaller f₁ is preferable in these regions to providemore “play” between the anchor elements and the surrounding tissue.Alternatively, the wound closure device is configured so that it doesnot elongate, but rather does not change its length along the long axis720.

The variation in the force profile around the periphery of the woundclosure device can be achieved in a variety of ways, such as varying thespacing/density of the tissue anchors, the types of anchors, length ofanchors, or configuration thereof, etc. For example, in FIGS. 9A and 9B,anchors 701 a, 701 b are longer and penetrate deeper into the tissuecompared to anchors 703 a, 703 b. The force profile can also be variedby controlling the vacuum force distribution in the filler material,such as by varying the pore size and/or pore density of the filler.

On one embodiment, a method of fabricating a wound closure device of theinvention includes forming a stabilizing endoskeleton of rigid orsemi-rigid material and forming a collapsible filler material over theendoskeleton. The stabilizing endoskeleton can be formed using a moldingprocess, and can be molded as an integral unit or in one or morecomponents that are then assembled to form the endoskeleton. Differentcomponents of the endoskeleton can have different thicknesses and/ordegrees of rigidity to provide varying levels of rigidity andflexibility along different directions. The endoskeleton can beassembled by joining components, such as by using a suitable adhesive orother joining process such as by inserting rods into tubular segments.In certain embodiments, at least some of the components can be assembledto provide articulating joints. In preferred embodiments, the fillermaterial is formed by mixing together appropriate metered amounts ofconstituent substances, (e.g., isocyanates, polyols, catalysts,surfactants, blowing agents and the like in the case of polyurethanefoam), dispensing the reacting mixture into a mold, and then curing anddemolding the material. Optionally, the material can then be cut ortrimmed to the finished shape. In preferred embodiments, theendoskeleton support structure is assembled and placed into the mold,and the filler material is molded around the endoskeleton. An example ofa biodegradable foam product suitable for the present wound closuredevice, and methods of fabricating such a foam, is described in U.S.Published Application No. 2009/0093550 to Rolfes et al., the entirecontents of which are incorporated herein by reference.

A method of performing a surgical procedure 800 using a wound closuredevice in accordance with preferred embodiments of the invention asillustrated in FIG. 10A. After preparation 800 of the patient forsurgery, an incision is made 820 to expose the surgical site, typicallyin the abdomen. After the procedure is performed, the wound is prepared830 for closure. The proper size and shape of the wound closure deviceis selected 840 with the peripheral tissue attachment members positionedaround the circumference or outer wall surface of the device. The deviceis inserted 850 into the wound and the tissue attachment elements areinserted 860 into the tissue. Negative pressure is then applied 870 toexert a closure force on the wound edges. Depending on the particularapplication, large wounds may require placement 880 of a smaller secondclosure after removal of the first larger device. Finally, the device isremoved 890 and the wound is closed, typically by suturing.

In a preferred embodiment in which tissue anchors are not used, a method900 for wound closure is described in connection with FIG. 10B. In thisembodiment the patient is prepared for surgery 1910, an incision orother means are used to open or expose 920 the wound and the procedureis performed 930. The wound closure device suited for the shape of thewound is selected 1940 and inserted 950 into the wound. In thisembodiment, the wound closure device flexes or expands under itsinherent expansion characteristics to contact the wound margins. Thewound is then sealed 960 and negative pressure is applied 970.Sufficient negative pressure is applied so that the expansion forceexerted by the device on the wound margin is less than the closure forceapplied to the wound and the device such that the wound closes at acontrolled rate. This provides a procedure in which the device maintainscontact with the wound margin and thereby reduces the occurrence oftyping of the device within the wound during closure. As in priorembodiments, the device can be replaced 980 as needed prior to woundclosure 990, however, the need for replacement is reduced by preventingthe formation of gaps between the wound margins and the device.

Certain types of wounds that can be treated with negative pressure woundtherapy involve the separation by incision of subcutaneous tissue toform a wound opening. This procedure is frequently used to accessunderlying structures, organs or injuries. The lateral displacement ofsubcutaneous tissue can contribute additional difficulties for thetreatment of the resulting wound.

Illustrated in FIG. 11A is a wound incision 900 in which tissue region906,908 have been separated to access an underlying tissue region 902for treatment. The lateral displacement of regions 906, 908 from theirrespective positions overlying region 902 has caused further separationbetween the displaced regions 906, 908 and the underlying structure. Inthe case of an open abdominal wound, the underlying structure can be thelarge and small intestines, which can be subject to infection and/orelevated fluid pressure.

Additionally, there can be separation between the fascia 909, 911 andabdominal muscle and the overlying subcutaneous tissue 906, 908.Consequently in FIG. 11A, the system can optionally include threecomponents, the pad 907 positioned between the abdominal cavity 902 andthe fascia that can be used to permit sliding movement and utilizenegative pressure, secondly, a seroma pad 925, described in greaterdetail hereinafter, positioned between the fascia and overlying tissueand, thirdly, the wound closure element 918. The negative pressureregion 918 can be in fluid communication with the underlying layer 925,which extends laterally to sections 914 and 916 which are situatedbetween overlying tissue 906, 908, respectively, and the underlyingabdominal muscle and fascia structure 911, 909. One or both sides of thesections 914, 916 can have tissue anchors 926, 928 as describedpreviously. Dotted line 921 indicates a region through which negativepressure is applied to all three layers.

After insertion of layer 925, the compressible wound closure element 918is inserted followed by sealing drape 905 and the closer device 940 andfluid control tube 942. The pad 907 operates to drain fluid 910 from theabdominal cavity by negative pressure through elements 925 and 918.

In the case where adjoining tissues need treatment utilizing negativepressure or require stabilization such as by pad 925, a wound treatmentsystem can be used in combination with the systems and methods describedherein. Shown in FIG. 11B is a top view of a system utilizing a negativepressure closure system 918 as described generally herein and a seromapad or tissue adhesion element 925. The shape of pad 925 can also becircular and be without apertures or tissue anchors, for example. Thenumber of drains can be in a range of 6-10 that extend in a radialdirection with uniform angular spacing between the drain elements.

Thus a preferred embodiment of the present invention provides a pad orsurgical drain device 925 for the prevention and treatment of seromas aswell as for general use in promoting drainage of surgical wounds andwound closure. The drain device can include a plurality of drain tubes935 disposed on a substrate termed an “adhesion matrix,” which isdesigned to promote tissue adhesion within the seroma or wound space.The adhesion matrix has a conformable configuration and is made of acompliant material having planar surfaces that can bend to adapt to theshape of the wound space.

In a preferred embodiment, the adhesion matrix contains a plurality ofapertures 927, or gaps in the matrix material, which allow tissuecontact across the matrix, so as to promote adhesion and wound closure.Thus, a tissue surface on a first side of the matrix can directlycontact a tissue surface on a second, or opposite, side of the matrix topromote rapid healing and stabilization of the wound. The number, sizeand distribution of the apertures 927 extending through the matrix canbe selected based on the geometry of the wound. For abdominal wounds,for example, the drain tubes can be positioned in a fan shaped arraywith a plurality of three or more tubes extending from a manifold. Thematrix and/or the tubing can be cut or shaped by the user to conform tothe shape of the wound. The matrix can also be used as a medicationcarrier to assist in the administration of a drug to a patient. Thematrix can optionally include a layer of adhesive on at least a portionof any of its surfaces. The drain tubes can be removed from the deviceonce drainage flow is sufficiently reduced, and the adhesion matrix canremain within the body, where it is degraded and absorbed over time,remaining in place to optimize tissue healing. The matrix can comprise aporous biodegradable polymer material. As the plurality of tubes extendfrom a single exit site into the wound with spaced apart distal ends, auser can readily remove all the tubes simultaneously from the wound.

As shown in more detail in FIG. 11C, the surgical drain device 925 caninclude a tissue anchoring system, whereby the device is mechanicallyattached to surrounding tissues by an array of surface barbs or hooks926, 928. These surface structures can be located on any exposed surfaceof the adhesion matrix. When the device is implanted, the surroundingtissues can be pressed against the barbs or hooks to embed them withinthe tissue and anchor the device. The use of surface barbs or hooks canbe used in combination with a surgical adhesive, providing a muchstronger bond between tissue layers than the adhesive alone, andproviding temporary adhesion while the adhesive sets. The structure ofthe hooks can have various forms depending on the tissue they areintended to bind. Longer hooks can be used for loosely bound tissuessuch as fat or connective tissue, while shorter hooks can be used fordenser tissues such as muscle. Anchors with more rigid stems can beutilized to penetrate denser tissues.

Another aspect of the invention is a system for surgical wound drainage.The system includes the drain device coupled to a wound closure device918 as described generally herein together with a vacuum source, such asa pump, and a tube connecting the vacuum source to the drain tubes ofthe drain device. The system optionally also can include a fluid trap tocollect drained fluid and a control unit to monitor and control theapplication of vacuum and the collection of fluid. Further components ofthe system can include a vacuum or pressure gauge, a flow meter, and acomputer to monitor vacuum and flow and to regulate vacuum or flow. Thepressure measurement can be used to control the level of appliedpressure using a feedback control circuit. The wound closure device 918can include the endoskeleton structure as described herein havingexternal ribs extending from the outer surface and flexure arms or beamsthat have an intrinsic restoring force that varies as a function ofposition of each flexure element. The different flexure elements canhave different restoring force depending upon their position within thestructure as shown in FIGS. 2A-3C, for example. The endoskeletonaccommodates expansion to fill the wound cavity and will collapse in awell-defined manner in response to the collapse of the wound undernegative pressure. As described herein, foam or other filler materialcan be used within the flexure system. The endoskeleton can have amultilayered structure with the different layers collapsing alongindividual planes of the three dimensional structure within the woundwithout tilting of the structure.

Another aspect of the invention is a method for treating or preventing aseroma, or promoting the drainage or closure of a surgical wound. Themethod includes positioning the drain device described above into aseroma, or a surgical wound, such as a wound at risk of forming aseroma, and allowing the device to drain fluid from the wound for aperiod of time. The device can include surgical adhesive and/or barbs orhooks on its surface to create adhesion between tissue layers within thewound and to anchor the device in place. Drainage can be by gravity flowor can be vacuum assisted by attaching a vacuum source to the draintubes of the device, using a manifold to merge the flow paths of thedrain tubes to a common drain tube for collection. Negative pressureapplied to the drain tubes can be used to hold the tissue layers aboveand below the device together until a surgical adhesive has set, oruntil the wound healing process binds the tissues together. Theapplication of negative pressure further facilitates contact betweentissue on opposite sides of the matrix through the apertures in thematrix to promote tissue adhesion. This improves the rate of healingwhile at the same time providing for drainage. Optionally, the draintubes of the device have apertures 933 extending along their length andcan be removed from the body after drainage flow is reduced, therebyreducing the burden for resorption by the body. Removal of the draintubes can be facilitated by the inclusion of drain tube channels, ordrain tube release tabs, within the adhesion matrix. Release of thedrain tubes is then accomplished by sliding the tubes out of thechannels or appropriately maneuvering the drain tube assembly to breakrelease tabs. The adhesion matrix is allowed to remain in the seroma orsurgical wound where it is resorbed over time.

The flow rate from the drain tubes can be regulated by flow controlelements. The flow rate can also be measured or the pressure of fluidscan be measured by ultrasound devices or by other methods. The systemcan also be used in conjunction with wound dressings that can also beattached to a negative pressure source to remove fluids from the wound.

A preferred embodiment of the of the invention includes a negativepressure wound closure device 1000 for the treatment of surgicallyrepaired ulcers as shown in FIG. 12. This type of wound often ischaracterized by a narrower wound opening 1001 that can have a generallycircular or oval shape. The surgeon can use this opening to accesstissue that must be removed to form a cavity 1005 that extendslaterally. A first wound closure element 1007 extends laterally toregions 1012, 1015 which can include tissue anchors 1014, 1016 thatserve to attach regions 1012, 1015 to tissue flaps 1004, 1006 above theregions 1012, 1015, respectively, as well as the underlying tissue 1026.The anchors 928 can also extend in a lateral direction. The second woundclosure element 1020, as described previously, is in fluid communicationwith adhesion elements 1007, and enables the application of negativepressure to the channels 935 of regions 1012, 1015 that can be employedin the embodiment of FIG. 12. The closure element can include apertures927 that allow for tissue contact through regions 1012 and 1015 as theseelements compress under negative pressure.

Illustrated in FIG. 13 is a sensor system 180, 182 for measuring woundclosure force that can be exerted on the side walls of the tissue beingdrawn together. The sensor elements 180, 182 can be mounted to theinternal flexible frame 108 or endoskeleton of the system and measurethe amount of force exerted laterally on the tissue. For example, as thelevel of negative pressure applied to wound closure element 100 isincreased, the sensors measure the increased force exerted on the tissueby anchors 106. Additional sensor elements can be mounted on thesidewalls of device 100, to measure the force distribution across thesidewalls. The flexure elements 108 can have a selected resiliency toenable controlled collapse of the device 100.

Shown in FIG. 14 is a pressure sensor system positioned to measure thepressure on underlying tissue. The sensor elements 320, 322 can measurepressure at the sliding interface 303 or at the bottom of panel 301,which can measure the amount of negative pressure at the tissueinterface such as in the abdominal cavity. This can be used to monitordownward pressure on the abdominal cavity that can arise duringcompression of structure 104.

The systems in FIG. 13 and FIG. 14 can optionally include a feedbackcontrol system 1200 that controls a level and/or distribution ofnegative pressure within the system. Such a feedback system 1200 isshown in connection with FIG. 15. Sensors 180, 182 can be connected toprocessor housing 360 using cable 350 and pressure sensors 320 and/or322 can measure fluid pressure such that sensor data are transmitted toprocessor housing 360 using cable 352. A data processor 366 can beprogrammed to adjust the applied pressure via tube 121 to prevent injuryto the patient and optimize the rate of wound healing. Data can bedisplayed on display 362 and a control panel 364 provides a userinterface for operation of the system.

FIG. 16A illustrates a further exemplary embodiments of a wound closuredevice 2100 of the present invention. The device 2100 includes a woundfiller material 2102 that is sized and shaped to fit within a woundopening 2201 of a human or animal patient. The device 2100 is furtherassociated with a negative pressure source 2120, such as described withrespect to FIGS. 1A-1F, which may be coupled to the filler material2102, e.g., by a suitable coupling or conduit. As noted above, negativepressure source 2120 can be activated to apply a negative pressure tothe filler material 2102. In general, the negative pressure causes aresulting pressure differential which causes the device 2100 to contractor “collapse.”

FIG. 16B depicts a pull apart view of the exemplary wound closure device2100 of FIG. 16A. The exemplary device 2102 advantageously includes astabilizing structure 2101, e.g., an endoskeleton structure such asdescribed above, and a collapsible filler material 2102, e.g., foam orother filler material as described herein, over the stabilizingstructure 2101. As depicted the filler material 2102 includes aplurality of sections of 2102A-D, configured for association with (e.g.,sized and shaped to match) each of a top surface 2101A, a bottom surface2101B, a first side surface 2101C and a second side surface 2101D of thestabilizing structure or moveable frame 2101. Thus, the sections 2102A-Dof the filler material 2102 cooperate to surround the stabilizingstructure 2101, e.g., forming a shell around the stabilizing structure2101, such as depicted in FIG. 17. The device can have a covering layer2105 that is used to contact at least the wound margins so that thelayer extends around the external surface of the filler 2102. Inexemplary embodiments, the stabilizing structure 2101 and the sections2102A-D of the filler material 2102 may be configured to define a cavityfor facilitating application of a negative pressure to device 2100,e.g., using negative pressure source 2120.

In some embodiments, each section 2102A, 2102B, 2102C or 2102D of thefiller material 2102 can define a plurality of surface features 2103 onthe inner peripheral surface thereof. For example, each of the depictedsections 2102A, 2102B, 2102C or 2102D of compressible material 2102defines an “egg crate” pattern of protrusions 2103A and 2103B valleys.Advantageously, the surface features 2103 defined on the innerperipheral surface of the sections 2102A-D of the filler material 2102may be configured for operative association with an inner volume ofstabilizing structure 2101.

As described in previous sections, each surface 2101A, 2101B, 2101C or2101D of the stabilizing structure 2101 may define a lattice pattern ofstructural elements including frame or stabilizer elements in the x-yplane (such as stabilizer elements 2108 of FIGS. 1A-1F) and stabilizerelements in the z axis (such as stabilizer elements 2110 of FIGS.1A-1F). Thus, the surface features 2103 defined on the inner peripheralsurface of each section 2102A, 2102B, 2102C or 2102D of the fillermaterial 2102 may be configured, e.g., patterned, to match the latticepattern of the corresponding surface 2101A, 2101B, 2101C or 2101D of thestructural element 2101. For example, as depicted in FIG. 16, thesurface features 2103 defined on the inner peripheral surface of the topand bottom sections 2102A and 2102B are configured such that the valleys2103B correspond to the stabilizer elements in the x-y plane. Similarly,the surface features 2103 defined on the inner peripheral surface of thefirst and second side sections 2102C and 2102D are configured such thatthe valleys 2103B correspond to the stabilizer elements in the z axis.Thus the protrusions 2103A or pattern elements extend into an innervolume of the structural element 2101, thereby providing tensile forcesto the stabilizing structure 2101, e.g., during the collapse thereof. Inexemplary embodiments, the filler material 2101 may be configured toprovide a pre-stress to the stabilizing structure 2101.

In some embodiments, the tensile forces applied by protrusions 2103 amay facilitate a structured collapse of the structural element 2101,e.g., in one or more directions. For example, the surface features 2103defined on the inner peripheral surface of each section 2102A, 2102B,2102C or 2102D of the filler material 2102 may be configured to impart apre-selected force profile to the stabilizing structure 2101, e.g.,during the collapse thereof. In some embodiments, the pre-selected forceprofile may control the collapse of the structural element 2101, e.g.,providing for a non-uniform collapse of filler material such as byresisting collapse in one or more directions and/or in one or moreregions. With reference to FIGS. 18A-18B, different force profileconfigurations for individual protrusions or elements 2103A aredepicted. In FIG. 18A the protrusion 2103A is configured to resistcompression of the associated stabilizer elements 2108 of the structuralelement 2101 in both x and y directions. Thus, the protrusion isconfigured to provide uniform tensile forces to the stabilizingstructure 2101, e.g., during the collapse thereof, in both the x and yaxis. In FIG. 18B, the protrusion 2103A is configured to provide greatercompression resistance of the associated stabilizer elements 2108 of thestructural element in the y direction than in the x direction. Thus, theprotrusion is configured to provide greater tensile forces to thestabilizing structure 2101, e.g., during the collapse thereof, in the yaxis than in the x axis. In a further embodiment, a smaller protrusion2103A is used to provide a delayed or a lower resistance to compressionrelative to the larger protrusion 2103A. The pattern elements fromadjacent regions within the frame preferably contact each other tofacilitate fluid flow under negative pressure. Thus, some regions of thestabilizing structure 2101 can be configured to collapse earlier orquicker than other regions while maintaining fluid flow.

With reference to FIG. 19, exemplary embodiments, side sections 2102Cand 2102D of the filler material 2102 may include a tissue graspingsurface 2104, such as tissue grasping surface 2104 of FIGS. 1A-1F,extending over an outer peripheral surface of the wound filler material2102. Note alternatively, that a separate covering layer of materialsuch as a film or mesh as described previously can extend around theouter surfaces of the wound filler. This layer can also include tissueanchors in a further preferred embodiment as described herein such thatthe device can adhere to the wound margins. Tissue grasping surface 2104may be an integral part of the filler material or may be a separatelayer, e.g., secured to the filler material 2102 using any suitabletechnique. In exemplary embodiments, grasping surface 2104 may include aplurality of tissue anchor elements 2106 configured to engage the tissueat a wound margin. Thus, with reference to FIG. 20A, when the fillermaterial 2102 is placed within a wound 2200, the anchor elements 2106become buried within the tissue at the wound margins 2203 and secure thedevice 2100 within the wound opening 2201. As the filler material 2102contracts, the tissue grasping surface 2104 grabs and pulls on theadjacent tissue, which is preferably the tissue around the wound margins2203, resulting in the displacement of the tissue thereby facilitatingthe closure of the wound.

While the invention has been described in connection with specificmethods and apparatus, those skilled in the art will recognize otherequivalents to the specific embodiments herein. It is to be understoodthat the description is by way of example and not as a limitation to thescope of the invention and these equivalents are intended to beencompassed by the claims set forth below.

What is claimed is:
 1. A negative pressure wound therapy device,comprising: a porous foam material that is sized and shaped forpositioning relative to a wound having wound margins wherein the porousfoam material has a length, width, and height with a pore size and apore density such that fluid is drained from the wound through theporous foam material upon application of negative pressure, the porousfoam material being structured to preferentially contract along at leasta first x-direction relative to a second y-direction upon application ofa negative pressure to the wound to apply a closure force to the woundmargins along the first x-direction.
 2. The negative pressure woundtherapy device of claim 1, further comprising a negative pressure sourcethat is coupled to the porous foam material with a tube to apply theclosure force to the wound.
 3. The negative pressure wound therapydevice of claim 1, wherein the porous foam material has verticalelements that inhibit contraction in a z-direction extending along theheight.
 4. The negative pressure wound therapy device of claim 1,further comprising a film that is provided over a surface of the porousfoam material.
 5. The negative pressure wound therapy device of claim 4,wherein the film comprises a mesh material extending along the surfaceof the porous foam material.
 6. The negative pressure wound therapydevice of claim 1, wherein the porous foam material further comprises aplurality of spaced elements wherein the elements contract towards alongitudinal axis extending in a length direction to enable contractionin at least the first x-direction and inhibit collapse in at least thesecond y-direction.
 7. The negative pressure wound therapy device ofclaim 6, wherein the spaced elements comprise one or more regions ofrigid material and regions of compressible material.
 8. The negativepressure wound therapy device of claim 6, wherein the spaced elementsinhibit collapse in a height dimension.
 9. The negative pressure woundtherapy device of claim 6, wherein the spaced elements comprise astabilizing structure that compresses the porous foam material in atleast the first x-direction to effect reapproximation of the wound. 10.The negative pressure wound therapy device of claim 6 wherein the spacedelements comprise a plurality of connected articulating elements. 11.The negative pressure wound therapy device of claim 6 wherein the porousfoam material has an oval shape or rectangular shape.
 12. The negativepressure wound therapy device of claim 1 wherein the porous foammaterial manages fluid within the wound such that the porous foammaterial slides over an underlying tissue during contraction.
 13. Thenegative pressure wound therapy device of claim 1 wherein the porousfoam material has regions of rigid material and regions of compressiblematerial and wherein the porous foam material has different regions withvariable pore sizes and/or pore densities.
 14. The negative pressurewound therapy device of claim 1 wherein the porous foam materialcomprises a molded material.
 15. The negative pressure wound therapydevice of claim 1 wherein the porous foam material comprises apolyurethane.
 16. The negative pressure wound therapy device of claim 1wherein the porous foam material is positioned relative to a line ofincision of the wound in a region of a dermis layer of a patient, thewound being sealed with a drape.
 17. The negative pressure wound therapydevice of claim 1 further comprising a negative pressure source coupledto the porous foam material with a tube to apply a negative pressure of125 mm to 250 mm through a port to the porous foam material.
 18. Thenegative pressure wound therapy device of claim 1 wherein the porousfoam material comprises predetermined lines to change a shape of theporous foam material.
 19. The negative pressure wound therapy device ofclaim 1 wherein the porous foam material has cleavage lines to alter atleast one of a size and shape of the porous foam material.
 20. Thenegative pressure wound therapy device of claim 1 wherein the porousfoam material comprises an outer wall surface that contracts in sizefrom an initial size to a reduced size upon application of negativepressure.
 21. A negative pressure wound therapy device comprising: aporous foam material that is sized and shaped for positioning relativeto a wound wherein the porous foam material has a length, width, andheight with a pore size and a pore density such that fluid is drainedfrom the wound through the porous foam material upon application ofnegative pressure, the porous foam material being structured topreferentially contract along at least a first x-direction relative to asecond y-direction upon application of a negative pressure to the woundto apply a closure force to wound edges of the wound along the firstx-direction; and a port to couple a negative pressure source to theporous foam material through a wound drape.
 22. The negative pressurewound therapy device of claim 21, further comprising a negative pressuresource that is coupled to the porous foam material with a tube to applythe closure force to the wound.
 23. The negative pressure wound therapydevice of claim 21, wherein the porous foam material has verticalelements that inhibit contraction in a z-direction extending along theheight direction.
 24. The negative pressure wound therapy device ofclaim 21, further comprising a film that is provided over a surface ofthe wound filler material.
 25. The negative pressure wound therapydevice of claim 24, wherein the film comprises a mesh material extendingaround the surface of the porous foam material.
 26. The negativepressure wound therapy device of claim 21, wherein the porous foammaterial further comprises a plurality of spaced elements wherein thespaced elements contract towards a longitudinal axis to enablecontraction in at least the first x-direction and inhibit collapse in atleast the second y-direction.
 27. The negative pressure wound therapydevice of claim 26, wherein the spaced elements comprise one or moreregions of rigid material surrounded by regions of compressiblematerial.
 28. The negative pressure wound therapy device of claim 26,wherein the spaced elements inhibit collapse in a height dimension. 29.The negative pressure wound therapy device of claim 26, wherein thespaced elements comprise a stabilizing structure that compresses theporous foam material in at least the first x-direction to effectreapproximation of the wound.
 30. The negative pressure wound therapydevice of claim 26 wherein the spaced elements comprise a plurality ofconnected articulating elements.
 31. The negative pressure wound therapydevice of claim 21 wherein the porous foam material has an oval shape ora rectangular shape.
 32. The negative pressure wound therapy device ofclaim 21 wherein the porous foam material manages fluid within the woundsuch that the porous foam material slides over an underlying layerduring contraction.
 33. The negative pressure wound therapy device ofclaim 21 wherein the porous foam material has regions of rigid materialand regions of compressible material and wherein the porous foammaterial has different regions with variable pore sizes and/or poredensity.
 34. The negative pressure wound therapy device of claim 21wherein the porous foam material comprises a molded material.
 35. Thenegative pressure wound therapy device of claim 21 further comprising aporous interface layer of material configured to lie between the porousfoam material and an underlying tissue.
 36. The negative pressure woundtherapy device of claim 21 wherein at least one of the pore size or poredensity is varied to control a vacuum force distribution within theporous foam material.
 37. The negative pressure wound therapy device ofclaim 21 wherein the device is configured to attach to a dermis layer ofthe patient to apply the closure force to the dermis layer.
 38. A methodfor treating a wound with negative pressure comprising: connecting asource of negative pressure to a porous foam material having a pore sizeand a pore density such that a tube couples the source of negativepressure to a port in a sealing drape; the porous foam material havingan interface layer on a bottom surface of the porous foam material, theinterface layer having pores to pass fluid through the interface layer;applying negative pressure to a wound with the porous foam material thatis sized and shaped with a length, width and height to apply a closureforce to opposing wound edges of a linear incision through a portion ofskin of a patient; and collapsing the porous foam material in a widthdirection in response to the application of negative pressure to theporous foam material.
 39. The method of claim 38 wherein the step ofapplying negative pressure with the porous foam material furthercomprises positioning the porous foam material over tissue wherein alayer of the porous foam material extends between the tissue and theporous foam material.
 40. The method of claim 38 wherein the porous foammaterial has an oval shape or a rectangular shape.
 41. The method ofclaim 38 wherein the porous foam material comprises an open cellpolyurethane foam.
 42. The method of claim 38 wherein the porous foammaterial further comprises a plurality of stabilizer elements.
 43. Themethod of claim 38 further comprising sensing a fluid pressure withinthe sealing drape.
 44. The method of claim 43 further comprisingcontrolling the applied negative pressure in response to the sensedfluid pressure.
 45. The method of claim 38 further comprising measuringthe closure force applied to the wound edges and controlling thenegative pressure source to adjust the applied closure force.